The marine electric motor is made up of electrical machinery and devices which by using and consuming electricity produce mechanical energy. The electromotive plant consists of an electric motor, power and management systems and control system. According to the type of electricity used to run them they are divided into DC and AC electric motors. Of the total electricity consumption on board the electromotive plants consume between 75 and 95% (depending on the type of ship). This group of consumers includes the electric winch drives, pump, compressor, fan and various auxiliary equipment necessary for the operation of the main engines. Among the most important factors in the evaluation of electric motors, like the majority of marine equipment, as it directly reduces the capacity of the ship, are their weight and dimensions. With large built-in engines, the possibility of on the spot repairs is very important. Preventive maintenance should be as simple as possible, including appropriate expertise of the crew, and in no case should interfere with the technological process, which means that it must be executed during the stay in the port, or that it does not require stopping the system. DC motors have almost ideal external engine characteristics which connect the rotation speed and developed torque, they have the ability to easily obtain a variable DC voltage power supply, they are easy to control and regulate and have a wide range of handling the speed of rotation. The work of the DC electric motor is based on the creation of the electromagnetic force in a guide which is located in the magnetic field. Electric motor AC (ie, AC motor) can be asynchronous and synchronous. Will the engine operate as synchronous or asynchronous depends on how the rotor is implemented. Stators of a synchronous and asynchronous motor are no different. Currents need to be created by a rotating magnetic field. Like transformers, asynchronous motors can have three types of electrical faults: ground connection, short circuits and interruption of circuit currents. Today, the synchronous motor is mainly used as part of regulated electromotive plants which means that they are powered from inverters, which are in the best possible way guided by slowly raising the frequency and voltage by controlling the position of the rotor. Electric motors must have overvoltage protection, short circuit protection and overload protection. A power surge occurs when the electrical circuit is closed through a man and at the same time expires current that exceeds his threshold of sensation (0,6-3mA). However the most dangerous electric shock is when the circuit is closed through the heart (hand-arm and hand-foot) and when there is no visible injuries death by heart failure can occur. The most important and most used technical measures to protect against electric shock is grounding of the ship, which in the case of ships, is more correctly called equalization potential.